<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="UTF-8" />
		<meta http-equiv="X-UA-Compatible" content="IE=edge" />
		<meta name="viewport" content="width=device-width, initial-scale=1.0" />
		<title>Document</title>
	</head>
	<body>
		<script>
			var obj = {
				name: 'abc',
				friend: {
					eatting: function () {
						console.log('eatting something')
					},
				},
			}

			console.log(obj.a) // undefined
			// 避免对象中没有某一个属性
			obj && obj.friend && obj.friend.eatting()
		</script>
	</body>
</html>
